The invention relates to an optical navigation device based on production on wafer scale, in which both the illumination path and the imaging lens system are integrated on a common carrier structure. The optical navigation devices according to the invention are used for controlling a cursor on an image output device or in the field of finger navigation.
In the case of optical navigation sensors, a surface region of the so-called tracking surface is illuminated as homogeneously as possible by a source for electromagnetic radiation, e.g. an LED or a laser diode, and corresponding beam-forming lens system. Subsequently, by means of an objective lens, either the illuminated tracking surface is imaged directly (in the case of the LED) or the speckle pattern produced by the reflection on the tracking surface (in the case of the laser diode) is imaged on a digital image sensor. The image recording takes place in a very rapid sequence (1,500-6,000 images per second) in succession. Successively recorded images are correlated with each other and the displacement of the images amongst each other, with reference to representative structures of radiation which is scattered or refracted on the tracking surface, is used as a measure for the size and speed of the displacement of the input device relative to the tracking surface or of a reference object relative to the input device. This is converted in turn into the movement of the mouse pointer on a display.
Miniaturisation of such an optical navigation sensor can be subdivided in steps in miniaturisation of the imaging lens system and miniaturisation of the illuminating lens system. Consequently, both lens systems must be miniaturised in common in order to achieve as great a total miniaturisation as possible.
For miniaturisation solely of the imaging lens system, the multichannel arrangement described in DE 10 2007 042 984 may be cited.
Furthermore, single-channel optical arrangements for illumination, as also for imaging the tracking surface, are known. As a result of the progressive miniaturisation and the short focal intercepts resulting therefrom, these incur however corresponding disadvantages in principle.
Problems now arise with the given diagonal of the image sensor during miniaturisation of the optical construction, since a reduction in constructional length for the outer image regions involves very large angles relative to the optical axis of the lens system (reverse imaging) and consequently the resolution of the imaging is greatly reduced because of off-axis aberrations and the brightness is greatly reduced because of the natural vignetting at the image edge.
To the same degree, the shortening of the existing construction represents a requirement for the illumination path since a shortening of the total construction means not only a shortening of the lens system imaging the tracking surface but also of the object distance. As a result of a smaller object distance, in the case of the present configuration, the illumination radiation would beam in at a very flat angle onto the tracking surface, which leads to a non-homogeneous illumination and reduced efficiency (usable radiation/emitted radiation). Furthermore, a large number of reflections of the illumination radiation is necessary, which leads to increased scattering and false light and hence reduces the image contrast. Furthermore, the separation of the imaging and illuminating lens system limits further miniaturisation.
Starting herefrom, it was the object of the present invention to provide an optical navigation device which eliminates the disadvantages known from the state of the art and presents a miniaturised device which enables, on the one hand, homogeneous illumination of the object to be imaged and efficient imaging onto the image sensor.
This object is achieved by the optical navigation device having the features of claim 1 and the input device having the features of claim 23. In claim 25, uses according to the invention are indicated. The further dependent claims reveal advantageous developments.